Process for preparing cf3cf2chrcl



United States Patent Ofiice 3,371,123 Patented F eb. 27, 1968 ABSTRACTOF THE DISCLOSURE This invention relates to a new process for preparing1,1,1,2,2-pentafluoro 3 chloro-3-bromopropane by treatingl,l,1,2,2-pentafluoro-3,3-dichloropropane with an inorganic bromide saltin the presence of a non-protic solvent, such as N,N-dimethylformamideor N,N-dimethylacetamide.

1,1,1,2,Z-pentafluoro-3-chloro-3-bromopropane (CF CF CHBrCl) is a knowncompound possessing anesthetic activity, which previous to thisinvention has been prepared by a number of methods, most of whichinvolve a reaction conducted at high temperature, i.e. 450-600 C. Thehigh temperature leads to the formation of a large number of by-prodnetsand these contaminants are diflicult to remove by conventionaldistillation techniques from the desired CF CFgCHBI'CI.

It has now been found that the compound can be prepared from1,1,l,2,2-pentafluoro-3,3-dichloropropane at a comparatively lowtemperature by reacting the dichloropropane with an inorganic bromidesalt in the presence of a non-protic solvent, such as an N,N-di(loweralkyl)- (lower alkanoic acid amide), e.g., N,N-dimethylformamide andN,N-dimethylacetamide. By use of these reactants, the desired1,1,1,2,2-pentafluoro-3-bromo-3-chloropropane is obtained insubstantially pure form since the reaction is carried out attemperatures below about 200 C. and preferably at about 60 C. to about175 C., and optimally at about 811 C. to about 150 C.

Among the suitable inorganic bromide salts can be mentioned the alkalimetal bromides, such as lithium bromide, potassium bromide, rubidiumbromide and cesium bromide; the alkaline earth metal bromides, such ascalcium bromide, strontium bromide and barium bromide; and, preferably,ammonium bromide and sodium bromide.

The reaction is preferably carried out employing at least one mole ofbromide salt per mole of CF CF CHCl The following examples illustratethe invention (all temperatures being in Centigrade):

Example 1 A mixture of 600 g. of dry N,N-dimethylformamide and 98.4 g.of dried ammonium bromide in a pressure vessel is stirred at 95 untilhomogeneous. Into the stirred mixture under pressure is introduced CF CFCHCl at the rate of g./min. maintaining the temperature at 90- 150. When203 g. of the CF CF CHCl has been introduced, the vessel is sealed andthe stirring and heating at 90-150 continued for about 10 hours. Thevessel is cooled, the contents discharged, and fractionated to giveabout 227.5 g. of CFgCFgCHBICl, B.P. about 70.270.5, with a purity of99.5%.

Example 2 To a suspension of 103 g. of dried sodium bromide in 601) ml.of dry N,N-dimethylforma;mide at room temperature is added 203 g. of CFCF CHCl- The mixture is stirred vigorously and heated slowly until theinternal temperature reaches about and the temperature is maintained atabout 80 for 8 hours. Eflicient cooling is required in the condenser toprevent loss of the volatile reactant and product. The mixture iscooled, the condenser is replaced by a fractionating column and thereaction mixture distilled, first to remove about 23 g. of

B.P. about 44.5", and then to collect about 233.2 g. of CF CF CHBrCl,B.P. about 70.2-70.5 with a purity of 99.7%.

Example 3 By substituting 213 g. of cesium bromide for the sodiumbromide and 500 ml. of dry N,N-dimethylacetamide for theN,N-dimethylformamide in Example 2, there is obtained about 199.3 g. ofCF CF CHBrCl, B.P. about 70.2- 70.5", with a purity of 99.4%.

Example 4 By substituting 138 g. of barium bromide for the sodiumbromide in Example 2, there is obtained about 160.3 g. of CF -CF CHBrCl,B.P. about 70.2-70.5", with a purity of 99.2%.

The invention may be variously otherwise embodied within the scope ofthe appended claims.

What is claimed is:

1. A process for preparing l,1,1,2,2-pentailuoro-3-bromo-3-chloropropane, which comprises interacting 1,1,l,2,2-pentafiuoro-3,3-dichloropropane with an inorganic bromide saltselected from the group consisting of ammonium bromide, alkali metalbromides and alkaline earth metal bromides in the presence of anon-protic solvent at a temperature of about 60 C. to about 175 C.

2. The process of claim 1, wherein the reaction is carried out at atemperature of about 911 C. to about C.

3. The process of claim 2, wherein the salt is ammonium. bromide.

4. The process of claim 3, wherein the solvent is N,N-dimethylformamide.

5. The process of claim 2, bromide.

6. The process of claim 2, wherein the solvent is N,N-dimethylacetamide.

wherein the salt is sodium References Cited UNITED STATES PATENTS3,287,425 11/1966 Maynard 260653.3 3,288,877 11/1966 Taylor et al260653.3

DANIEL D. HORWITZ, Primary Examiner.

